Monomer for use in preparation of a polymer to be used in optical devices

ABSTRACT

A monomer having general Formula (I) which may be substituted or unsubstituted: where E and E are the same or different and are reactive groups capable of undergoing chain extension; X is O, S, NR 5 , R 5 C—CR 6  or R 5 ═CR 6 ; Y is O, S, NR 7 , R 7 C—CR 8  or R 7 C═CR 8 ; R 5 , R 6  R 7  and R 8  are the same or different and each is independently H or a substituent group; and each Ar is the same or different and is independently a substituted or unsubstituted aryl or heteroaryl group.

[0001] The present invention relates to a novel compound, specifically anovel monomer for use in the preparation of a polymer.

[0002] A polymer prepared from a monomer according to the presentinvention is envisaged to be useful in an optical device such as anoptical device comprising an electroluminescent device or a photovoltaicdevice.

[0003] Electroluminescent devices are structures which emit light whensubjected to an applied electric field. In its simplest form anelectroluminescent device comprises a light-emissive layer between twoelectrodes. The cathode electrode injects negative charge carriers(electrons) and the anode electrode injects positive charge carriers(holes) into the light-emissive layer. Light emission occurs when theelectrons and holes combine in the light-emissive layer to generatephotons. As a practical aspect, one of the electrodes. is typicallytransparent, to allow the photons to escape the device. Thelight-emissive layer should be made from a light-emissive material whichmay- be laid down as a film without substantially affecting theluminescent characteristics of the material and which is stable at theoperational temperature of the device.

[0004] The colour of the light generated by the light-emissive materialis determined by the optical gap or semiconductor bandgap of thelight-emissive material. The semiconductor bandgap of the light-emissivematerial is the difference in energy between the “highest occupiedmolecular orbital” (HOMO) and the “lowest unoccupied molecular orbital.”(LUM0) levels. Effectively, the semiconductor bandgap is the energydifference between the valance and conduction bands of thelight-emissive material. These levels can be estimated by photoemissionmeasurements and measurements of the electrochemical potentials foroxidation and reduction of the light-emissive material. However, thelevels of these energies are affected by numerous factors. Accordingly,the use of such values is indicative rather than quantitative

[0005] PCT/WO90/13148 discloses an electroluminescent device comprisinga semiconductor layer comprising a polymer film as the light-emissivelayer which comprises at least one conjugated polymer. In this case, thepolymer film comprises a poly(para-phenylene vinylene) (PPV) film.

[0006] EP 0544795 discloses the use of a semiconductive conjugatedcopolymer as the light-emissive layer in an electroluminescent device.The semiconductive conjugated copolymer comprises at least twochemically different monomer units which, when existing in theirindividual homopolymer forms, typically have different semiconductorbandgaps. The proportion of the chemically different monomer units inthe copolymer can be selected to control the semiconductor bandgap ofthe copolymer so as to control the optical properties of the copolymer.To some degree, the extent of conjugation of the copolymer can be saidto affect the bandgap of the copolymer. Increasing the extent ofconjugation has the effect of decreasing the bandgap up to the point ofbandgap convergence. Therefore, selection of an appropriate polymerstructure is one way of selecting the bandgap. This gives the verydesirable feature of controlling the colour of the light output from thepolymer when made to emit light. This property is useful particularly inthe construction of the electroluminescent devices.

[0007] Polymers are known that are capable of emitting ‘red light’whenused in an electroluminescent device. For example, embodiment onedescribed in PCT/GB00/00911 relates to “red light emission”. It isfurther stated that light having a wavelength in the range 600 nm to 700nm is obtainable with polymers according to embodiment one. WO 00/46321is concerned with fluorene copolymers and electronic devices (such aspolymer light-emitting diodes) containing one or more films derived fromthe copolymers. It is stated in Table 4 that copolymer 19 can be used inan LED that emits red light. A bandgap of 2.10 electron volts is givenin Table 2 for copolymer 19.

[0008] It can be seen that there exists a deficiency in the prior art ofsemiconductive polymers capable of “deep red” emission i.e. red lighthaving a longer wavelength, above 700 nm and towards the IR end of thespectrum when used in an electroluminescent device. It will beunderstood from the above that the wavelength of emission from asemiconductive polymer when used in an electroluminescent device will beinfluenced by its structure. Furthermore, it will be understood from theabove that the solubility of a semiconductive polymer will be limited byits structure. The structure of a polymer is derived from the monomersfrom which it is made. Thus, a deficiency exists in the prior art ofmonomers that are suitable for making a polymer that is capable of “deepred” emission or capable of other wavelengths of emission, particularly“red” emission.

[0009] It is an aim of the present invention to overcome at leastpartially the deficiencies of the prior art and to provide such polymersparticularly for use in an optical device. To be used in an opticaldevice, such polymers also desirably have good optical devicecharacteristics. These characteristics include the internal quantumefficiency (number of photons generated relative to the number of chargecarriers injected into the polymer), the solubility and processabilityof the material and the lifetime when used in a device. Also relevantfor consideration is the stability of the polymer during use and storageof the device.

[0010] As a result of extensive research into polymer structure, thepresent inventors have found that such a polymer may be prepared from amonomer having general formula I which may be substituted orunsubstituted:

[0011] where E and E′ are the same or different and are reactive groupscapable of undergoing chain extension; X is O, S, NR₅, R₅C—CR₆ orR₅C═CR₆; Y is O, S, NR₇, R₇C—CR₈ or R₇C═CR₈; R₅, R₆, R₇ and R₈ are thesame or different and each is independently H or a substituent group;and each Ar is the same or different and is independently a substitutedor unsubstituted aryl or heteroaryl group.

[0012] Accordingly, a first aspect of the present invention provides amonomer having general formula I:

[0013] where E and E′; X; Y; R₅, R₆, R₇ and R₈ and each Ar are asdefined above.

[0014] A second aspect of the present invention provides a polymerprepared from a monomer according to the first aspect.

[0015] A third aspect of the present invention provides a polymercomprising a first repeat unit comprising a unit having general formulaV that is substituted or unsubstituted:

[0016] where X, Y and Ar are as shown or defined in the first aspect,provided that none of the Ar groups comprise a mono fluorene group.

[0017] A fourth aspect of the present invention provides the use of apolymer according to the second or third aspect in an optical device.

[0018] A fifth aspect of the present invention provides the use of arepeat unit having general formula V that is substituted orunsubstituted for accepting and combining positive and negative chargecarriers to generate light in a part of a polymer, where X, Y and Ar areas shown or defined in the first aspect of the present invention.

[0019] A sixth aspect of the present invention provides a method formaking a polymer according to the second aspect.

[0020] A seventh aspect of the present invention provides an opticaldevice comprising a polymer according to either the second or thirdaspects.

[0021] Referring to the first aspect of the present invention, themonomer is a “pentamer”. Such a “pentamer” has not been providedpreviously as part of a monomer for the preparation of a polymer.

[0022] For the purposes of the present application, the dashed circlesin formula I or any other formula in the present application may betaken to indicate that each of the fused rings include sufficient doublebonds in positions suitable to satisfy the valency of the atoms in thering.

[0023] Preferably, each Ar group independently is substituted orunsubstituted and is selected from the group consisting of phenylene,thiophene, furan, pyridene, pyrrole, quinoxaline, benzothiadiazole,benzofuranodiazole, benzotriazole, and other diazines and 1,3,5triazines. These preferred Ar groups include the following:

[0024] Z=S, O or N—R

[0025] R=H or a substituentd group, preferably C-₁₋₁₀ alkyl

[0026] Also, preferably each Ar group independently is substituted orunsubstituted and is a heteroaryl group.

[0027] A preferred monomer, having preferred Ar groups is a monomerhaving general formula II:

[0028] where E, E′, X, Y, R₅, R₆, R₇ and R₈ are as defined above inrelation to the first aspect of the present invention and each Z is thesame or different and is independently O, S, NR or RC═CR and each R, R₁,R₂, R₃ and R₄ is the same or different from any one of the other R, R₁,R₂, R₃ and R₄ groups and each is independently H or a substituent group.

[0029] Preferred groups of general formula II are shown in generalformulas III and IV:

[0030] where E, E′, Z, R₁, R₂, R₃, R₄, R₅, R₆, R₇ and Re are as-definedabove in relation to general formula II.

[0031] Preferred groups of general formula III are shown in generalformula VIII to X, where R₁, R₂ and R₃ are substituent groups and E andE′ are as defined in relation to general formula III.

[0032] Preferred central groups of the “pentamer” in the first aspectinclude the following:

[0033] where Y=S, O or N—R₇ and R₅, R₆ and R₇ are the same or differentand each independently is H or a substituent group, preferably H orC₁₋₁₀ alkyl or any other preferred substituent group defined in relationto general formulae II to IV. For ease of manufacture in central group(ii) above, the Ph substituents are positioned on the diazole ringrather than the benzene ring.

[0034] Referring to general formulae II, III, IV, VIII, IX and X,independently, preferred R, R₁, R₂, R₃, R₄, R₅, R₆, R₇ and R₈ groupsinclude hydrogen or an optionally substituted hydrocarbyl group. Theterm “hydrocarbyl” is intended to include alkyl, alkenyl, alkynyl andaryl groups. A discussion of the effect of substituents on molecularorbital energy levels (HOMO and LUM0 levels) can be found in Chapter 2of Color Chemistry (Synthesis, Properties. and Applications of OrganicDyes and Pigments) by Heinrich Zollinger (2^(nd) edition, 1991, VCHPublishers, Inc., New York, N.Y. (USA)). Preferred substituents may beelectron donating or electron withdrawing substituents depending on thepreferred effect on the bandgap of a polymer prepared from the monomer.Other preferred substituents include solubilising groups i.e. asubstituent that improves the solubility in a common organic solvent,toluene, xylene or THF of a polymer derived from the monomer.

[0035] Independently, preferred R, R₁, R₂, R₃, R₄, R₅, R₆, R₇ and R₈substituent groups include amine, cyano, alkyl, aryl, heteroaryl,alkoxy, thioalkyl, perhaloalkyl, alkylaryl, arylalkyl, alkyloxy,aryloxy, alkoxyaryl or alkoxy heteroaryl groups.

[0036] In a particularly preferred embodiment, at least one or more thanone of the R₁, R₂, R₃ and R₄ groups is an unsubstituted C₁₋₁₀, alkyl oralkoxy group. Such groups will increase the solubility of such apolymer.

[0037] Thus, in general formulae III, VIII, IX or X, independently,preferred R₁, R₂, R₃ and R₄ groups and also preferred R₅ and R₆ groupsinclude hydrogen and C₁₋₁₀, alkyl or alkoxy. As mentioned above C₁₋₁₀,alkyl or alkoxy group substituents can be used to improve the solubilityof a polymer derived from the monomer. Furthermore, the electronicproperties of the hydrogen or C₁₋₁₀, alkyl or alkoxy group substituentsare useful in selecting the bandgap of a polymer derived from themonomer. Suitably, C₁₋₁₀ alkyl or alkoxy substituent groups are providedon the inner Ar groups.

[0038] In general formula IV, it is preferred that R₇ and R₈ are thesame and are both a substituted or unsubstituted phenyl group.

[0039] As mentioned above, in the present monomer, each Ar group may bethe same or different. However, for ease of manufacture, it is preferredthat each Ar is the same.

[0040] It is preferred that one or more of the Ar groups comprises oneor more solubilising group substituents.

[0041] In the monomer according to the first aspect of the presentinvention, it is preferred that E and E¹ are the same or different andare selected from the group consisting of a reactive halide functionalgroup and a reactive boron derivative group. Specifically, the reactivehalide functional group is selected from the group consisting of F, Cl,Br and I and the boron derivative group is selected from the groupconsisting of a boronic acid group, a boronic ester group and a boranegroup.

[0042] The use of a monomer according to the first aspect of the presentinvention for the preparation of a polymer is provided. Typically, thepolymer will be provided as a component, preferably a light-emissivecomponent, in an optical device.

[0043] According to the second aspect of the present invention a polymerprepared from a monomer as defined above in the first aspect of thepresent invention is provided.

[0044] Also, in the third aspect of the present invention there isprovided a polymer comprising a first repeat unit comprising a unithaving general formula V which is substituted or unsubstituted:

[0045] where X, Y and Ar are as defined above in relation to the firstaspect of the present invention, with the proviso that none of the Argroups comprise a mono fluorene group. The nature of a mono Fluorenegroup is such that a polymer comprising a first repeat unit comprising aunit having general formula V where one or more of the Ar groupscomprised a mono fluorene group would not have a very low bandgap aswill be typical for many polymers according to the second aspect of thepresent invention.

[0046] For the purposes of the present invention, the term a “monofluorene” group may be taken to include any substituted or unsubstitutedgroup as shown below:

[0047] where each R independently is H or a substituent group andeach*indicates a linking position linking the fluorene group to thepolymer chain and the fluorene group is not linked at either linkingposition to another fluorene group. Mono fluorene groups are excludedbecause they do not allow useful tuning of the polymer's electronic andphysical properties. A mono-fluorene group in the polymer backbonesimply can be viewed as a linker group that is not capable of usefullytuning the polymer's electronic and physical properties for the purposesof the present invention. Furthermore, polymers having mono-fluorenegroups in the polymer chain tend to have a lower Tg and also are proneto aggregation.

[0048] In a further embodiment of the third aspect of the presentinvention, none of the Ar groups comprise a fluorene group.

[0049] It has been found that in a polymer having a repeat unit derivedfrom a monomer according to the first aspect of the present invention,the arrangement of the substituted or unsubstituted aryl or heteroarylgroups (Ar groups) leads to a polymer having a lower bandgap as comparedwith a polymer derived from a ‘trimer’ monomer having general formula:

[0050] This lowering of the bandgap is extremely useful for preparingpolymers having a very low bandgap, for example, capable of emittingradiation in the IR region. Furthermore, it is extremely useful forovercoming to some extent the sacrifice in emission colour which mayresult from the inclusion of solubilising moieties in the polymerderived from the above ‘trimer’ monomer.

[0051] Polymers according to the second or third aspect of the presentinvention will have a wider range of possible emission wavelengths ascompared with a polymer derived from the above ‘trimer’ monomer and thuswill have a wider field of application, beyond the field ofelectroluminescent display devices.

[0052] In a preferred embodiment of the second or third aspect of thepresent invention, the polymer comprises a second repeat unit Ar₁ thatis a substituted or unsubstituted aryl or heteroaryl group. It ispreferred that, in a polymer comprising a second repeat unit Ar₁, thepolymer comprises a repeat unit having formula VI that is substituted orunsubstituted:

[0053] Ar¹ may be selected from the group consisting of a substituted orunsubstituted, fused or unfused, benzene, thiophene, furan, fluorene,triarylamine, bistriarylamine or pyridine group. More preferably, thesecond repeat unit is selected from the group consisting of a 2,3-, 2,5-or 2,6-substituted benzene; 3,4-substituted thiophene; 3,4-substitutedfuran; 9,9-disubstituted fluorene; unsubstituted pyridine; benzo-,thio-,or furano-2,3-substituted diazine; unsubstituted phenothiadiazine or anunsubstituted triarylamine or bistriarylamine group.

[0054] Polymers according to the second or third aspect of the presentinvention may comprise a homopolymer, copolymer, terpolymer or higherorder polymer. In this regard, a repeat unit is distinguished from aresidual monomeric unit. A homopolymer (i.e. prepared by polymerisationof a single type of monomer) may be defined to have more than onedifferent repeat unit. Where the polymer is not a homopolymer, it may bea random or regular alternating polymer.

[0055] Where the present polymer is a copolymer, it is preferred that itis a 1:1 copolymer. A preferred comonomer in a copolymer comprises afluorene group.

[0056] Further preferred polymers according to the second and thirdaspects of the present invention further comprise a third repeat unitAr₂ that is a substituted or unsubstituted aryl or heteroaryl group. Apreferred third repeat unit has general formula VII that is substitutedor unsubstituted:

[0057] where X′ is O or S. A particularly preferred polymer in thisregard has a repeat unit as shown in general formula VI and a repeatunit as shown in general formula VII.

[0058] Generally, it is preferred that a polymer according to the secondor third aspect of the present invention comprises up to about 50 mol %of a unit having general formula V. More preferably, the polymer willcomprise from 0.1 mol % to 50 mol %, more preferably from 5 mol % to 10mol % of the unit.

[0059] As mentioned above, the components of a polymer according to thesecond or third aspect of the present invention, can be selected so thatthe polymer has a very low bandgap. Such polymers are particularlyuseful since many are capable of emitting light at a wavelength in therange 550 nm to 1000 nm, particularly 700 to 800 nm or 800 to 1000 nm.

[0060] From the nature of the first repeat unit, it will be clear thatat least a part of the backbone of a polymer according to the second orthird aspect of the present invention will be conjugated. Preferably,the polymer backbone will be partially, substantially, or even fullyconjugated.

[0061] A polymer according to the second or third aspect of the presentinvention will have a degree of polymerisation of at least 3.

[0062] Typically, a polymer according to the second or third aspect ofthe present invention will have a molecular weight of at leastM_(n)=about 10,000 daltons. Preferably, they will have an averagemolecular weight in the range 10,000 to 10⁶.

[0063] Typically, a polymer according to the second or third aspect ofthe present invention will be soluble in common organic solvents such astoluene, xylene and THF. Such polymers conveniently can be laid down asa film from solution.

[0064] Accordingly, a film comprising a polymer according to the secondor third aspect of the present invention also is provided.

[0065] Furthermore, a coating comprising a polymer as defined in thefirst or second aspect of the present invention is provided.

[0066] Still further, a composition comprising a mixture which comprisesa polymer as defined in the first or second aspect of the presentinvention is provided. Preferably, the mixture comprises one or twofurther, different polymers.

[0067] A polymer according to the second or third aspect of the presentinvention is envisaged to be useful as a component in an optical device,particularly a light-emitting device. A particularly preferred use is asa component in an electroluminescent device.

[0068] The very low bandgap that is obtainable for a polymer accordingto the second or third aspect of the present invention means that thepolymer also may be used as a component in a photovoltaic device oroptoelectronic device such as a solar cell. It also may be used in aninfra-red emitting polymer LED such as a sensor, remote control,detector.

[0069] Other uses include the use of the polymer as a component in aphotoluminescent device, a waveguide, a dye composition, a sensor, anelectrochemical cell or a fibre.

[0070] In this regard, the present invention also provides the use of arepeat unit having general formula V that is substituted orunsubstituted for accepting and combining positive and negative chargecarriers to generate light in a part of a polymer.

[0071] According to a sixth aspect of the present invention, there isprovided a method for making a polymer according to the second or thirdaspect of the present invention which includes the step of reacting in areaction mixture a first monomer and a second monomer. The first andsecond monomers may be the same or different from one another. Furthersteps may involve a reaction with further monomers.

[0072] Several different polymerisation methods are known which may beused to manufacture polymers in accordance with the second and thirdaspects of the present invention.

[0073] One particularly suitable method is disclosed in Internationalpatent publication No. WO 00/53656, the contents of which areincorporated herein by reference. This describes the process forpreparing a conjugated polymer, which comprises polymerising in areaction mixture (a) an aromatic monomer having at least two reactiveboron derivative groups selected from a boronic acid group, a boronicester group and a borane group, and an aromatic monomer having at leasttwo reactive halide functional groups, or (b) an aromatic monomer havingone reactive halide functional group and one reactive boron derivativegroup selected from a boronic acid group, a boronic ester group and aborane group, wherein the reaction mixture comprises a catalytic amountof a catalyst (e.g. palladium) suitable for catalysing thepolymerisation of the aromatic monomers, and an organic base in anamount sufficient to convert the reactive boron derivative functionalgroups into active polymerisable units, particularly —BX₃ ⁻ anionicgroups, wherein X is independently selected from the group consisting ofF, alkoxy and OH.

[0074] Polymers according to the present invention which have beenproduced by this method are particularly advantageous. This is becausereaction times are short and residual catalyst (e.g. palladium) levelsare low.

[0075] Another polymerisation method is disclosed in U.S. Pat. No.5,777,070. The process involves contacting monomers having two reactivegroups selected from boronic acid, C1-C6 boronic acid ester, C1-C6borane and combinations thereof with aromatic dihalide functionalmonomers or monomers having one reactive boronic acid, boronic acidester or borane group and one reactive halide functional group with eachother.

[0076] A further polymerisation method is known from “Macromolecules”,31, 1099-1103 (1998). The polymerisation reaction involvesnickel-mediated coupling of dibromide monomers. This method commonly isknown as “Yamamoto Polymerisation”.

[0077] According to one embodiment of the sixth aspect of the presentinvention there is provided a process for preparing a polymer as definedabove in relation to the second or third aspect of the present inventionwhich includes polymerising in a reaction mixture:

[0078] (a) a first aromatic monomer comprising a first repeat unit asdefined above in general formula V and at least two reaction boronderivative groups selected from a boronic acid group, a boronic estergroup and a borane group; and

[0079] (b) a second aromatic monomer comprising further of the firstrepeat unit and/or a second repeat unit Ar₁ and at least two reactivehalide functional groups,

[0080] wherein each boron derivative group is selected from a boronicacid group, a boronic ester group and a borane group and wherein thereaction mixture comprises a catalytic amount of a catalyst suitable forcatalysing the polymerisation of the aromatic monomers, and an organicbase in an amount sufficient to convert the reactive boron derivativefunctional groups into —BX₃ ⁻ anionic groups, wherein X is independentlyselected from the group consisting of F, alkoxy and OH.

[0081] A further process according to the sixth aspect of this inventionfor preparing a polymer as defined above in relation to the second orthird aspect of the present invention also is provided which includespolymerising in a reaction mixture:

[0082] (a) a first aromatic monomer comprising a first repeat unit asdefined above in general formula V and one reactive halide functionalgroup and one reactive boron derivative group; and

[0083] (b) a second aromatic monomer comprising further of the firstrepeat unit and/or a second repeat unit Ar₁, and one reactive halidefunctional group and one reactive boron derivative group,

[0084] wherein each boron derivative group is selected from a boronicacid group, a boronic ester group and a borane group and wherein thereaction mixture comprises a catalytic amount of a catalyst suitable forcatalysing the polymerisation of the aromatic monomers, and an organicbase in an amount sufficient to convert the reactive boron derivativefunctional groups into —BX₃ ⁻ anionic groups, wherein X is independentlyselected from the group consisting of F, alkoxy and OH.

[0085] In a final aspect of the present invention, there is provided anoptical device or a component therefore, which comprises a substrate anda polymer according to the second or third aspect supported on thesubstrate.

[0086] A device according to the present invention may be prepared inaccordance with the disclosure of WO 99/48160, the contents of which areincorporated herein by reference. Polymers according to the second orthird aspect of the present invention may be present in the device asthe sole light emitting polymer or as a component in a blend furthercomprising hole and/or electron transporting polymers. Alternatively,the device may comprise distinct layers of a polymer of the presentinvention, a hole transporting polymer and/or an electron transportingpolymer.

[0087] In one embodiment, the optical device comprises anelectroluminescent device. Specifically, the electroluminescent devicecomprises a first charge injecting layer for injecting positive chargecarriers, a second charge injecting layer for injecting negative chargecarriers, a light-emissive layer located between the first and secondcharge injecting layers comprising a light-emissive material foraccepting and combining positive and negative charge carriers togenerate light wherein the light-emissive layer comprises a polymer asdefined in the first or second aspects for accepting and combiningpositive and negative charge carriers or for transporting positiveand/or negative charge carriers from the first and/or second chargeinjecting layer to the light-emissive material. In one embodiment, thepolymer according to the present invention is provided as thelight-emissive material.

[0088] It will be appreciated that the light-emissive layer may beformed from a blend or mixture of materials including one or morepolymers according to the present invention, and optionally furtherdifferent polymers. As mentioned above, usually, the polymer accordingto the present invention will be included for accepting and combiningpositive and negative charge carriers to generate light. The furtherdifferent polymers may be so-called hole transport polymers (i.e. toimprove the efficiency of hole transport to the light-emissive material)or electron-transport polymers (i.e. to improve the efficiency ofelectron-transport to the light-emissive material). Preferably, theblend or mixture would comprise at least 0.1% by weight of a polymeraccording to the present invention, preferably from about 0.2 to about50% more preferably from about 0.5% to about 30% by weight.

[0089] Alternatively, a polymer according to the present invention maybe provided in an electroluminescent device as discrete layer situatedbetween the first and second charge injecting layers. Where thisdiscrete layer is included for accepting and combining positive andnegative charge carriers to generate light it optionally may be incontact with one or more hole and/or electron transporting layers.

[0090] The present invention now will be described in further detailwith reference to the attached drawing in which:

[0091]FIG. 1 is a schematic diagram of an electroluminescent deviceaccording to this invention;

[0092]FIG. 2 shows absorption spectra; and

[0093]FIG. 3 shows photoluminescence spectra.

[0094] “Pentamer” monomers of formula I may be prepared from the“trimer” monomers disclosed in WO 00/46321 and in PCT/GB01/00019(incorporated herein by reference). Pentamer monomers may be prepared byessentially the same methodology used to generate the “trimer” monomersdisclosed in this prior art, as outlined below:

[0095] Alkylated pentamer monomers may be prepared via alkylation of themonomer precursors as outlined below:

[0096] DiBr-DMBT

[0097] DiBr-MBT

[0098] 3-Hexyl Thiophene

[0099] Polymers according to the present invention may be prepared bySuzuki polymerisation as disclosed in WO 00/53656 (incorporated hereinby reference). In one particular example, the polymer is prepared frommonomers 7, 8 and 9 shown below present in a ratio of 50:25:25.

[0100] Alternatively, the polymer may consist of a 1:1 co-polymer ofdioctylfluorene and a pentamer.

EXAMPLE 1

[0101] Preparation of Pentamer Monomers

Pentamer R1 R2 R3 R4 R5 R6 1 H H C₆ H H H 2 C₆ H C₆ H H H 3 C₆ H H H H H

[0102] (A) Synthesis of Pentamer 1

[0103] Step 1 (Stille-Coupling)

[0104] Trimer 7 was prepared in accordance with the method disclosed inWO 01/49768.

[0105]2-(Tributylstannyl)thiophene (22.34 g, 59.9 mmol), trimer 7 (15.00g, 23.9 mmol), and tetrakis(triphenyl-phosphine) palladium (0) (0.55 g,.2 mol %) in toluene (200 mL) was refluxed. The reaction was followed bytlc. (hexane eluent) After 18 h, the reaction was allowed to cool toroom temperature and was then filtered through silica. The filtrate wasevaporated to dryness and recrystalised from hexane to give 10.7 g(70.7% yield, ¹H nmr (CDCl₃/TMS) 7.98 (2H, s); 7.82 (2H, s); 7.34 (2H,dd); 7.23 (2H, dd); 7.10 (2H, dd); 2.78 (H4, t, J=7.8); 1.75-1.26 (20H);0.91 (H6, t, J=7.2). 99.6% by HPLC).

[0106] Step 2 (NBS bromination)

[0107] A suspension of the pentamer 1 precursor material (10.7 g, 16.9mmol) in DMF (200 mL) was dissolved by gentle heating. The solution wasallowed to cool to r.t. before starting dropwise addition (in theabsence of light) of N-bromosuccinimide (6.0 g, 33.8 mmol) in DMF (50mL). The reaction was stirred overnight before the product was filteredoff and washed (methanol, deionised water). Recrystallisation fromhexane gave 6.3 g (47% yield). Further material was obtained fromrecystallisation of the mother liquor. ¹H nmr (CDCl₃/TMS) 7.93 (2H, s);7.78 (2H, s); 7.01 (4H, dd,); 2.78 (H4, t, J=7.8); 1.75-1.26 (20H); 0.91(H6, t, J=7.2). 99.6% by HPLC).

[0108] (B) Synthesis of Pentamer 2

[0109] Step 1 (Stille-Coupling)

[0110] 3-Hexyl-5-tributylstannylthiophene (32.8 g, 71.8 mmol), trimer 7(15.0 g, 23.9 mmol), and tetrakis(triphenyl-phosphine) palladium (0)(0.55 g, 2 mol %) in toluene (200 mL) was refluxed. The reaction wasfollowed by tlc. (hexane eluent) After 18 h, the reaction was allowed tocool to room temperature and was then filtered through silica. Thefiltrate was evaporated to dryness and recrystalised from IPA to give15.8 g (82.4% yield).

[0111] Step 2 (NBS bromination)

[0112] This material was brominated identically as described forPentamer 1 in Example 1(A).

[0113] (C) Pentamer 3

[0114] This pentamer was prepared using same methods as pentamers 1 and2 in Examples 1(A) and 1(B).

[0115] Step 1 (Stille-coupling)

[0116] Yield 15.2g, 73.3%. ¹H nmr (CDCl₃/TMS) 8.02 (2H, d); 7.83 (2H,s); 7.23 (2H, d); 7.14 (2H, s); 6.85 (2H, s); 2.59 (H4, t); 1.90-1.28(20H); 0.91 (H6, t).

[0117] Step 2 (NBS bromination) Yield 13.4 g, 71.5%. ¹H nmr (CDCl₃/TMS)7.99 (2H, d, J=4.0); 7.82 (2H, s); 7.16 (2H, d, J=4.0); 6.98 (2H, s);2.56 (H4, t, J=8.0); 1.64-1.26 (20H); 0.91 (H6, t, J=8.0)

EXAMPLE 2

[0118] Preparation of Polymers

[0119] A polymer according to the invention was prepared according tothe method of W000/53656, in the presence of 10 mol % bromothiophene tolimit molecular weight, by reaction of9,9-di-n-octylfluorene-2,7-diethyleneboronate (1.9132 g, 3.6 mmol) andpentamer 1 (2.8526 g, 3.6 mmol) in toluene (40 ml). The crude polymerwas passed through a celite column, eluted with toluene and precipitatedin methanol to furnish the final polymer(9,9-di-n-octylfluorene-Pentamer 1). Final Mp˜23,000.

EXAMPLE 3

[0120] Electroluminescent Device

[0121] A suitable device structure is shown in FIG. 1. The anode 2 is alayer of transparent indium-tin oxide (“ITO”) supported on a glass orplastic substrate 1. The anode 2 layer has a thickness between 1000-2000Å, usually about 1500 Å. The cathode 5 is a Ca layer having anapproximate thickness of 1500 Å. Between the electrodes is a lightemissive layer 4 having a thickness up to about 1000 Å. The emissivelayer 4 comprises between 0.5 to 30% by weight of the present polymerwith the remainder of the emissive layer consisting of hole and/orelectron transport material and/or emissive material. Advantageously,the device includes a hole transport material layer 3 of PEDOT having athickness of about 1000 Å. Layer 6 is an encapsulant layer of a suitablethickness.

[0122] Experiment 1

[0123] Photovoltaic Application

[0124] An effective form of photovoltaic devices is that comprising ablend of an electron donor such as poly(3-hexylthiophene) (P3HT) and anelectron acceptor such as F8-trimer copolymer (below) as the activematerials. Photovoltaic devices comprising blends are discussed in U.S.Pat. No. 5,670,791.

[0125] In these devices, excitons formed on F8-trimer are ionized bytransfer of a hole to the P3HT, whereas excitons formed on P3HT aredissociated by transfer of an electron to F8-trimer:

[0126] A drawback of these blends with respect to their use as solarcells is that they do not absorb a significant fraction of solarradiation. However polymers according to the present invention absorb asignificantly larger proportion of radiation as illustrated bycomparison of absorption spectra of a blend of P3HT and F8-trimercopolymer with a blend of P3HT and polymer F8-pentamer 1 according tothe present invention. The absorption spectra are shown in FIG. 2.

[0127] In FIG. 2, the full line shows solar irradiance at the Earth'ssurface. The onset of absorption for the trimer containing copolymer isaround 610 nm (dotted line) whereas the onset of absorption for thepentamer copolymer is red-shifted by about 75 nm to around 685 nm(dashed line).

[0128] Experiment 2

[0129] PLED Application

[0130] As can be seen from the photoluminescence spectra shown in FIG.3, the luminescence of the F8-pentamer 1 copolymer is red-shifted bycomparison with the F8-trimer copolymer.

1. A monomer having general formula I which may be substituted orunsubstituted:

where E and E′ are the same or different and are reactive groups capableof undergoing chain extension; X is O, S, NR₅, R₅C—CR₆ or R₅C═CR₆; Y isO, S, NR₇, R₇C—CR₈ or R₇C═CR₈; R₅, R₆, R₇ and R₈ are the same ordifferent and each is independently H or a substituent group; and eachAr is the same or different and is independently a substituted orunsubstituted aryl or heteroaryl group.
 2. A monomer according to claim1, wherein each Ar independently is substituted or unsubstituted and isselected from the group consisting of phenylene, thiophene, furan,pyridene, pyrrole, quinoxaline, benzothiadiazole, benzofuranodiazole,benzotriazole, other diazines and 1,3,5 triazines.
 3. A monomeraccording to claim 2, having general formula II:

where E, E′, X, Y, R₅, R₆, R₇ and R₈ are as defined in claim 1 and eachZ is the same or different and is independently O, S, NR or RC═CR and R,R₁, R₂, R₃ and R₄ are the same or different and each is independently Hor a substituent group.
 4. A monomer according to claim 3, havinggeneral formula III:


5. A monomer according to claim 3, having general formula IV:


6. A monomer according to any one of claim 3 to 5, where each Z is thesame or different and is independently S or O.
 7. A monomer according toany one of the preceding claims, where each Ar is the same.
 8. A monomeraccording to any one of the preceding claims, where at least one Arcomprises at least one C₁₋₁₀ alkyl or C₁₋₁₀ alkoxy substituent group. 9.A monomer according to any one of the preceding claims, where E and E¹are the same or different and are selected from the group consisting ofa reactive halide functional group and a reactive boron derivativegroup.
 10. A monomer according to claim 9, where the reactive halidefunctional group is selected from the group consisting of F, Cl, Br or Iand the boron derivative group is selected from the group consisting ofa boronic acid group, a boronic ester group or a borane group.
 11. Apolymer prepared from a monomer as defined in any one of claims 1 to 10.12. A polymer comprising a first repeat unit comprising a unit havinggeneral formula V that is substituted or unsubstituted:

where X, Y and Ar are as shown or defined in any one of claims 1 to 8and provided that none of the Ar groups comprise a mono fluorene group.13. A polymer according to claim 12, wherein each Ar is the same ordifferent and each independently is a substituted or unsubstitutedheteroaryl group.
 14. A polymer according to any one of claims 11 to 13further comprising a second repeat unit Ar₁ that is a substituted orunsubstituted aryl or heteroaryl group.
 15. A polymer according to claim14 further comprising a third repeat unit Ar₂ that is a substituted orunsubstituted aryl or heteroaryl group.
 16. A polymer according to claim15 comprising a repeat unit having general formula VI and a repeat unithaving general formula VII:

where X′=O or S and X and Y are as defined in claim 12 and Ar is asdefined in any one of claims 1 to 8, 12 or 13 and Ar₁ is as defined inclaim
 14. 17. A polymer according to claim 14 or claim 15 where at leastone of Ar₁ and Ar₂ comprises a substituted or unsubstituted fluorenegroup or a substituted or unsubstituted benzothiadiazole group.
 18. Apolymer according to any one of claims 12 to 17 where the polymercomprises from 0.1 mol % to 50 mol % of the first repeat unit.
 19. Apolymer according to any one of claims 11 to 18, capable of emittinglight at a wavelength in the range 550 nm to 1000 nm.
 20. A polymeraccording to any one of claims 11 to 19 wherein the polymer backbone isfully conjugated.
 21. Use of a polymer as defined in any one of claims11 to 20 as a component in an optical device.
 22. Use of a polymeraccording to claim 21, wherein the optical device comprises anelectroluminescent device or a photovoltaic device.
 23. A filmcomprising a polymer as defined in any one of claims 11 to
 20. 24. Acoating comprising a polymer as defined in any one of claims 11 to 20.25. A composition comprising a mixture which comprises a polymer asdefined in any one of claims 11 to
 20. 26. A composition according toclaim 25, wherein the mixture comprises one or two further differentpolymers.
 27. Use of a repeat unit having general formula V that issubstituted or unsubstituted for accepting and combining positive andnegative charge carriers to generate light in a part of a polymer:

where X, Y and Ar are as shown or defined in any one of claims 1 to 8,12 or
 13. 28. A method for making a polymer which includes the step ofpolymerising in a reaction mixture: (a) a first aromatic monomercomprising a first repeat unit as defined in general formula V and atleast two reactive boron derivative groups selected from a boronic acidgroup, a boronic ester group and a borane group; and (b) a secondaromatic monomer comprising further of the first repeat unit and/or asecond repeat unit Ar₁ that is a substituted or unsubstituted aryl orheteroaryl group and at least two reactive halide functional groups,wherein the reaction mixture comprises a catalytic amount of a catalystsuitable for catalysing the polymerisation of the aromatic monomers, andan organic base in an amount sufficient to convert the reactive boronderivative functional groups into —BX₃ ⁻ anionic groups, wherein X isindependently selected from the group consisting of F, alkoxy and OH;and wherein general formula V is:

where X, Y and Ar are as shown or defined in any one of claims 1 to 8,12 or
 13. 29. A method for making a polymer which includes the steppolymerising in a reaction mixture: (a) a first aromatic monomercomprising a first repeat unit as defined in general formula V and onereactive halide functional group and one reactive boron derivative groupselected from a boronic acid group, a boronic ester group and a boranegroup; and (b) a second aromatic monomer comprising further of the firstrepeat unit and/or a second repeat unit Ar₁ that is a substituted orunsubstituted aryl or heteroaryl group, and one reactive halidefunctional group and one reactive boron derivative group selected from aboronic acid group, a boronic ester group and a borane group, whereinthe reaction mixture comprises a catalytic amount of a catalyst suitablefor catalysing the polymerisation of the aromatic monomers, and anorganic base in an amount sufficient to convert the reactive boronderivative functional groups into —BX₃ ⁻ anionic groups, wherein X isindependently selected from the group consisting of F, alkoxy and OH;and where general formula V is:

where X, Y and Ar are as shown or defined in any one of claims 1 to 8,12 or
 13. 30. An optical device or a component therefor, which comprisesa substrate and a polymer according to any one of claims 11 to 20supported on the substrate.
 31. An optical device according to claim 30,wherein the optical device comprises an electroluminescent device. 32.An optical device according to claim 31, wherein the electroluminescentdevice comprises: a first charge injecting layer for injecting positivecharge carriers; a second charge injecting layer for injecting negativecharge carriers; a light-emissive layer located between the first andsecond charge injecting layers comprising a light-emissive material foraccepting and combining positive and negative charge carriers togenerate light: wherein the light-emissive material comprises a polymeras defined in any one claims 11 to
 20. 33. An optical device accordingto claim 30, wherein the optical device comprises an optoelectronic orphotovoltaic device.
 34. Use of a monomer as defined in any one ofclaims 1 to 10, for the preparation of a polymer.
 35. Use of a monomeraccording to claim 34, wherein the polymer is provided as a component ofan optical device.
 36. Use of a monomer according to claim 35, whereinthe polymer is provided as a light-emissive component of an opticaldevice.